The present invention is directed to an optical device which may be used as an optical waveguide demultiplexer according to the diffraction grating principle or as an optical waveguide multiplexer. The optical device has a diffraction grating, optical means such as a reflecting mirror and first and second coupling surfaces which are provided in spatially separated image spaces of the mirror.
In optical wave demultiplexers having diffraction grating, an optical means for forming imaging optics and first and second coupling surfaces is disclosed, for example, in an article in Electron. Lett., Vol. 16, 1980, page 108.
From the literature, a series of waveguide demultiplexer components are already known which employ plane diffraction gratings in conjunction with a concave mirror or a lens or which use a concave diffraction grating. In contrast to plane gratings, concave gratings are complicated to manufacture.
Compact structures with concave mirrors are known for example, from an article by Belovolov et al, Third Intern. Conf. Integr. Opt. and Opt. Fiber Commun., San Francisco, 1981, Paper TUH2 and from an article by Laude et al, Opto, No. 3, 1981, p. 33. In these devices, the one or more incoming optical waveguides and the outgoing optical waveguides which waveguides may be optical glass fibers are closely spaced together and thus mutual adjustment is rendered more difficult. The same applies to gradient lens arrangements such as disclosed in an article by Kobayashi et al, Quant. Electr. QE-16, 1980, p. 11. Picture or illustration 6 of this article by Kobayashi clearly shows that the minimum spacing between an incoming fiber and an outgoing fiber will amount to approximately 50.mu.. In the case of translation or movement of the outgoing fibers, for example, which movement is necessary for an adjustment purpose, it is expected that the incoming fiber will also be inadvertently displaced.
In the construction according to the article by Laude et al in Opto, a bipartite grating or grating with an opening in the center was utilized. Such a construction is not desirable.
In an article by Watanabe et al, Electron. Lett., Vol. 16, 1980, p. 108, an arrangement which has the incoming fiber and the outgoing fibers being spatially separated is disclosed. However, the construction of this device is not very compact.